MetroHealthAnesthesiaAnesthesia and Hypothryoidism

Clinical Manifestations
    Etiology
      autoimmune disease (Hashimoto's thyroiditis)
      thyroidectomy
      radioactive iodine
      antithyroid medications
      iodine deficiency
      failure of the hypothalamic-pituitary axis (secondary hypothyroidism)
    Neonatal hypothyroidism -> cretinism with physical and mental retardation
    Adult manifestations
      weight gain
      cold intolerance
      muscle fatigue
      lethargy
      constipation
      hypoactive reflexes
      dull facial expression
      depression
      decreased heart rate, contractility, stoke volume, cardiac output
      cool, mottled extremities (peripheral vasoconstriction)
      pleural, pericardial, abdominal effusions
      low free T4
      TSH elevated in primary hypothyroidism
    Treatment
      thyroid hormone administration
      several days for physiologic effect
      weeks until definite clinical improvement
    Myxedema coma
      extreme hypothyroidism
      impaired mentation
      hypoventilation
      hypothermia
      hyponatremia (SIADH)
      CHF
      more common in elderly
      precipitating factors
        infection
        surgery
        trauma
      treatment
        intravenous thyroid hormone, T3 or T4, as bolus + infusion
        monitor ECG for ischemia and dysrhythmia
        hydrocortisone 100 mg IV Q8H (possible coexisting adrenal gland suppression)
        ventilatory support may be needed
Anesthetic Considerations
Preoperative
    Postpone elective surgery until correction of severe hypothyroidism (T4 < 1 mg%) or myxedema coma
    Slow gastric emptying
    Prone to drug-induced respiratory depression
    Continue usual thyroid hormone
Intraopreative
    Susceptible to induction hypotension with most agents
    If refractory hypotension, consider
      additional adrenal insufficiency
      CHF
    Ketamine may be good induction agent
    Inhalation induction faster with decreased cardiac output
    No significant effect on MAC
    Large tongue
    Other potential problems
      hypoglycemia
      anemia
      hyponatremia
      hypothermia
Postoperative
    Delayed emergence/recovery
      hypothermia
      respiratory depression
      slowed drug biotransformation
    May need prolonged ventilatory assistance
    Ketorolac



Send Comments to Greg Gordon MD, gjg@po.cwru.edu
Department of Anesthesiology
The MetroHealth System
2500 MetroHealth Drive
Cleveland, Ohio 44109-1998
Phone: (216) 778-4801
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